The problem of maintaining engine manifold cooling water at a temperature below boiling has established the need for a temperature sensitive circuitry to control cooling fans mounted on a locomotive.
Various types of automatic control circuits for controlling fans to provide temperature regulation are known in the prior art. One such system is disclosed in U.S. Pat. No. 3,332,621 (Automatic Control Means) which discloses a cam operated system for selectively closing the electrical contacts of associated motors to drive various fans in accordance with the desired temperature regulation.